The term "snap-fit latch," as used herein, refers to mechanisms which use interengaging male and female latch elements disposed on relatively movable first and second components to detachably and repeatably secure the two components together. Examples are container/lid combinations. The two components may be hinged together or totally separate.
The components are joined by bringing the two of them into registry to place the male and the female latch elements in alignment with one another, followed by a step of urging the components together such that contact between the latch elements alters one or both of the elements from an undeformed, at-rest condition. The geometry of the male and female latch elements is such that when the two components reach a desired orientation relative to one another the altered latch element is allowed to snap back, due to its own elasticity, to a comparatively undeformed condition wherein it is engaged with its mating latch element.
The resulting mechanical engagement between the latch elements prevents the joined components from being separated until the latch elements are manipulated in a manner to permit them to be easily disengaged from one another. This is normally accomplished by manually urging one or both of the latch elements back to the same deformed condition that permitted the two elements to become engaged with one another.
Snap-fit latch mechanisms thus rely on the elastic behavior of the latch elements as well as the geometries of those elements to ensure proper functioning of the latch. If the latch elements are too stiff and/or the amount of deflection required for them to reach engagement is too high, the mechanism requires the application of a large amount of force to both engage and disengage the latch. This is usually undesirable because it makes the latch mechanism difficult to manually operate, and/or because the high stresses applied to the latch elements can, after repeated use, cause permanent deformation such that the elements will no longer mate securely. On the other hand, if the lock elements are not stiff enough or do not require much deflection to disengage, the result may be a latch mechanism that does not hold securely and/or is prone to inadvertent release during use of the components.